The present invention is concerned with a brake pressure control, in particular for use with automotive vehicles, comprising an anti-locking control system (ABS) and/or a traction slip control system (ASR), which operates on a fluidic, especially hydraulic, pressure medium, the invention comprising a master cylinder, one or more wheel cylinders, a pressure modulator for changing the hydraulic pressure in the wheel cylinders during the brake pressure control mode, with the pressure modulator exhibiting at least one inlet valve and at least one outlet valve associated to a wheel cylinder, at lease one pressure fluid source, preferably a motor-driven pump, for generating a fluidic, especially hydraulic pressure, and an electronic controller.
Generically, the invention is based on brake systems of the type as described, for example, in German unexamined published application No. 3731603.
Brake systems of the afore-mentioned type are equipped with an anti-locking control system and/or a traction slip control system. They exhibit one or more auxiliary pumps. Such pumps deliver, during the antilocking control mode, pressure fluid in a pressure modulator.
The pressure modulator has a number of hydraulic valves, in particular, inlet and outlet valves that are associated with predetermined wheel cylinders.
The driver phase of the electronic controller controls the inlet and outlet valves in accordance with the control algorithm installed in the controller. With the outlet valve opened and the inlet valve closed, a pressure decrease phase is generated in the wheel cylinder. With the inlet valve closed and the outlet valve closed, a phase of constant pressure will be established. With the inlet valve opened and the outlet valve closed, a phase of pressure re-increase will be attained.
Moreover, a hydraulic circuit has been described wherein the inlet valve causes a throttling effect, see German Patent Application P 3919842.1.
The afore-mentioned Patent Application describes an anti-locking, hydraulic brake system for use with automotive vehicles, comprising a master cylinder, a pressure fluid collector, at least one wheel brake which, through a brake conduit, is in communication with the master brake cylinder and, through a return conduit, is in communication with the pressure fluid collector. An electromagnetically actuated outlet valve is also provided in the return conduit to block, in the resting position thereof, the return conduit and to open, in the switching position thereof, the return conduit. A throttle valve is provided in the brake conduit and has two switching positions, with an unthrottled connection to the wheel in a first switching position and a throttled connection existing in the second switching position. A pump takes in pressure fluid from the pressure fluid collector and delivers same through a pressure conduit, to the master cylinder. A sensor detects the angular velocity of the wheel to be decelerated, and an electronic analyzer analyzes the sensor signal and generates switching signals for the pump drive and the outlet valve.
According to the afore-mentioned German Patent Application it is suggested that by means of a control conduit the throttle valve is connected to the pump outlet so that the pressure on the pump outlet causes the throttle valve to switch from the first into the second switching position. During the control mode, according to the lattermentioned German Patent Application, a throttle provided in the inlet conduit leading to the wheel cylinder will become operative. During the control mode, pressure fluid is delivered by the pumps, through the throttle, into the wheel cylinder, thereby causing a pressure reincrease in the wheel cylinder.
The pressure decrease is attained through opening of an outlet valve The outlet valves are electromagnetically actuable valves closed in deenergized condition (SG-valves) Conventionally, such SG-valves are actuated by an output signal of the electronic controller of the anti-locking system.
The afore-mentioned German Patent Application, is deemed to constitute the prior state of art.
The following problems are sought to be solved by the present invention:
The state-of-the-art anti-locking systems equipped with electromagnetically actuated valves open in deenergized condition, so called SO-valves, forming the inlet valves, are intended to be replaced by simpler and less costly valves. The invention is to enable the inlet valves to be hydraulically actuated.
Another object of the invention resides in that, during normal deceleration, high pressure increase gradients be attained while maintaining a good pedal feeling. In the anti-locking control mode, high pressure decrease gradients are intended to be achieved in the pressure decrease phase.
The invention is desired to be suitably used with both closed and open systems Closed systems are those having no pressure fluid reservoir open to the atmosphere in their circuits while open systems do contain such pressure fluid reservoirs.
The invention is intended for use with all types of brake pressure control systems.